Matthew Montano <mmontano@xxxxxxxxx> wrote:
>Most large aircraft do have the capability, by the nature that as a %
>of their total weight, the fuel is a significant junk.
>
>DC-10s/MD-11s, as do 767s, 747s, 777s.
>
>Someone visualized it for me that if a large aircraft landed that was
>almost full of fuel (if it could hold any sort of glide path) would
>stop when the wheels touched the ground; but the wings would keep
>going.
>
>Boom.
>
>Not sure how true that would be though.
Any aircraft certified to FAR Part 25 should be able to do considerably
better than that. The landing gear and the rest of the structure should be able
to withstand landing loads generated by a vertical speed at touchdown of 10
ft/sec up to Max Landing Weight and 6 ft/sec up to Max Take-off Weight.
This requirement ensures that all airliners are structurally sound to
withstand a landing at Max Take-off Weight, provided the circumstances allow
a halfway decent landing. Any landing above Max Landing Weight will
nevertheless trigger a heavy-landing inspection, keeping the aircraft out of
service for a little while.
A fuel dump system is purely a performance issue. It is required, unless the
aircraft can maintain required approach and landing climb gradients at up to
full take-off weight. These climb requirements are intended to ensure that the
aircraft can climb away from an aborted approach, even with one engine
inoperative (provided the landing gear is still capable of retracting).
Formulated this way, it actually becomes a design trade-off: either fit a
fuel dump system, or provide some excess thrust. In practice this means that
most long-range airliners have fuel dump systems, while short-range aircraft do
not.
The foregoing should not be taken as a promotion of overweight landings; it
is just intended to debunk the myth that aircraft fall apart when landing
above Max Landing Weight. Operationally, it is a command decision to
accept the lesser of two evils: either spend the time to dump fuel or burn it
off, or accept the lower safety factor of an overweight landing.
Kees de Lezenne Coulander
C.M. de Lezenne Coulander
Aircraft Development and Systems Engineering B.V.
Hoofddorp, the Netherlands